The present invention relates generally to seal assemblies for effecting a seal between relatively movable parts and, more particularly, to an improved single-element seal assembly that prevents contamination from entering into the inner static area on the static side of the seal assembly.
Single-element seal assemblies, particularly for use in providing a seal between relatively movable or reciprocating surfaces such as pistons and surrounding cylinders and/or piston rods and surrounding housings, are generally well known in the art. The seal element is usually but not always formed from a relatively resilient, deformable sealing material, such as synthetic or natural rubber, and is generally annular. Typically, the seal element is installed in an annular sealing groove or gland within one of the reciprocating surfaces with the groove opening facing the other surface. Such single-seal elements are designed to seal both during low pressure operation, i.e. below a predetermined pressure limit, and during high pressure operation, i.e. at or above the predetermined pressure limit. In general, the pressure limit determines the specific material used to form the seal element.
While such a seal assembly generally provides effective sealing at both low and high pressures, the prior art seal element, due to its structure, tends to force or "pump" contaminants into the sealing groove behind the seal element and into an inner static area between the seal element and the surface of the sealing groove. Eventually, the accumulation of contaminants causes undue wear on the seal element within the groove and tends to force the seal element to move away from the back surface of the seal groove resulting in leakage on the static side of the seal element. As a result of such static side leakage, the seal is eventually compromised. The prior art seal element also has a disadvantage in that it tends to crack and break apart at the sealing face due to stress concentrations.
The present invention comprises an improved single-element seal assembly in which the seal element prevents contamination from entering into the inner static area between the seal element and the surface of the groove to maintain good sealing contact on the static side and to prevent undue wear of the seal element. Also, the improved seal element is designed to resist cracking and breaking apart at the sealing face.